As the development of communication technologies, especially the fast development of wideband communication technologies, various modulation methods of high spectral efficiency are widely used. However, the issue of high peak-to-average power ratio (PAPR) lays higher requirements on the linearization technology of a high-power amplifier (HPA).
In the linearization technology of an HPA, a digital pre-distortion technology is a method that is widely used and efficient. Its basic principle is to perform pre-distortion processing on transmitted signals by a pre-distorter with nonlinear characteristics contrary to those of an HPA before the signals passing through the HPA, so as to improve the nonlinear characteristics of the whole transmitter system and make the whole system to exhibit linear characteristics as possible.
The structure of a pre-distortion transmitter having a digital power control system is as shown in FIG. 1. The digital power control system controls the output power of the HPA via digital gains, changes of the digital gains have effect on power distribution of DPD input signals, and further on address distribution of a look-up table (LUT). This will result in some DPD coefficients under-trained or unfully trained under some power levels, making DPD properties deteriorated, and affecting DPD stability and resulting in abnormality of the operation of the whole transmitter in severe cases.
It should be noted that the above description of the background art is merely provided for clear and complete explanation of the present invention and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background art of the present invention.